Photovoltaic cells convert sunlight directly into electricity by the interaction of photons and electrons within a photoconducting material. To create a photovoltaic cell a photoconducting material, commonly silicon, is joined by electrical contacts to form a junction. Presently, most silicon-based photovoltaic cells are silicon p-n junction devices. Photons striking the cell cause the mismatched electrons to be dislodged creating a current as they move across the junction. A grid of these electrical contacts creates an array of cells from which the current is gathered. The DC current produced in the cell depends on the materials involved and the energy and intensity of the radiation incident on the cell.
Photovoltaic cells have been available for a number of years and it has been predicted that the use of photovoltaics will continue to increase for years to come. The major obstacles to photovoltaic use throughout the world are cell efficiency and cell cost. Presently, the cost per watt for most photovoltaic cells is not low enough for these cells to be competitive with other energy sources. Currently, single crystal silicon is the photovoltaic material of choice. Amorphous silicon is also used because it is less expensive; unfortunately it is also less efficient than single crystal silicon. Gallium arsenide cells are among the most efficient cells presently available, but they are quite expensive. Thus, a need exists for a photovoltaic cell that is both cost and energy efficient.